PROBLEM TO BE SOLVED : To reduce the amount of labor for architecture client by determining land, building designer, a construction agent, etc., by a bid by an initiative of the architecture client.SOLUTION : A computer of the architecture client wishing the construction of the building, a computer of a land owner or a mediation agent, a computer of building designer designing a building and a computer of a construction agent constructing the building are connected to an information management means managing an information via a communication network, such as the Internet. The land owner or the mediation agent provides a land information to the information management means via the communication network. The architecture client determines the land, the building designer and the construction agent by a bid via the communication network and the information management means.